Purpose: To identify patient populations at high risk for bone metastases at any time after diagnosis of operable breast cancer, because these patients are potential beneficiaries of treatment with bisphosphonates.
Patients and methods: We evaluated data from 6,792 patients who were randomized in International Breast Cancer Study Group clinical trials between 1978 and 1993. Median follow-up was 10. 7 years. A total of 1,275 patients (18.7%) presented with node-negative disease, whereas 3,354 patients (49.4%) had one to three and 2,163 patients (31.9%) had four or more involved axillary lymph nodes. We also assessed the incidence of subsequent bone metastases in the cohort of 1,220 patients who had a first event in local or regional sites or soft tissue alone. Median follow-up for this cohort was 7.7 years from first recurrence.
Results: For the entire population with operable disease, the cumulative incidence of bone metastases at any time was 8.2% at 2 years from randomization and 27.3% at 10 years. The highest cumulative incidences of bone metastases at any time were among patients who had four or more involved axillary nodes at the time of diagnosis (14.9% at 2 years and 40.8% at 10 years) and among patients who had as their first event a local or regional recurrence or a recurrence in soft tissue, without any other overt metastases (21.1% at 2 years from first recurrence and 36.7% at 10 years).
Conclusion: Treatments to prevent bone metastases may have a major impact on the course of breast cancer and may be most efficiently studied in populations with several involved axillary nodes at the time of presentation and in populations with local or regional recurrence or recurrence in soft tissue.